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Implementation of DSP-Based Adaptive Inverse Filtering System for ECTF Equalization

The Head Related Transfer Function (HRTF) and the inverse Ear Canal Transfer Function (ECTF) must be accurately determined if stereo earphones are realize out-of-head sound localization (OHL) with high presence. However, the characteristics of ECTF depend on the type of earphone used and the number of earphone mounting and demounting operations. Therefore, we present a DSP-based adaptive inverse filtering system for ECTF equalization in this paper. The buffer composition and size of DSP were studied so as to implement operation processing. As a result, we succeeded in constructing a system that was able to work in the audio-band of 15kHz with the sampling frequency of 44.1kHz. Listening tests clarified that the effective estimation error of the adaptive inverse-ECTF for OHL was less than -11dB with convergence time of about 0.3 seconds.